1. Field of the Invention
The present invention relates to a front sheet for solar cells, a method of manufacturing the same and a photovoltaic module including the same.
2. Discussion of Related Art
Recently, much attention has been paid to renewable and clean energy because of global environmental problems and exhaustion of fossil fuels. Among these, solar energy has attracted attention as a representative pollution-free energy source which can solve the problems of environmental contamination and exhaustion of fossil fuels.
A solar cell to which a principle of photovoltaic power generation is applied is a device configured to convert sunlight into electric energy. In general, the solar cell is manufactured from a monocrystalline, polycrystalline or amorphous silicon-based semiconductor, and has a basic structure similar to a diode.
Since the solar cell is exposed for a long time to external environments to facilitate absorption of sunlight, it is manufactured into a unit by performing several packaging processes to protect the cells. Such a unit is referred to as a photovoltaic module.
Generally, a photovoltaic cell should absorb as great a quantity of solar radiation energy as possible to enhance the efficiency the photovoltaic cell, but a large quantity of the solar radiation energy may be a major cause for increasing the temperature of a cell. The performance of the solar cell is degraded as an operating temperature increases. Thus, an increase in operating temperature of the solar cell should be suppressed to improve the efficiency of the photovoltaic module.
Although it is desirable for a photovoltaic module to receive a larger quantity of sunlight so as to generate a larger quantity of power, an infrared ray (IR) region of sunlight is hardly used to generate solar power, and may be a major cause for increasing the temperature of a cell, which leads to deteriorated efficiency of the solar cell. In general, a crystalline module and a thin film module have temperature coefficients of −0.5%/° C. and −0.25%/° C., respectively. Here, the temperature coefficient represents that the power generation efficiency is degraded as the temperature of a cell increases. Therefore, when the IR region of sunlight which is not required for generation of solar power is selectively blocked, an increase in temperature of the photovoltaic cell may be suppressed so that the power generation efficiency can be enhanced.
In this regard, there has been research conducted in the prior art to suppress an increase in temperature of a photovoltaic cell by depositing a transparent inorganic oxide on a side of the photovoltaic cell to which sunlight is incident so as to transmit visible rays (VRs) but block an IR region of sunlight. However, the technique has a problem in that the cost for a multi-layered vapor deposition process is very high.
Korean Patent Publication No. 2008-0029230 discloses a conventional technique using an IR blocking layer. However, the technique has a problem in that heat may be generated since IRs are blocked by absorption, or the transmittance may be deteriorated within a VR region due to poor selectivity at a certain wavelength range.
Therefore, there is continuous demand for a material for photovoltaic modules which is able to maintain transmittance at a VR region, effectively suppress an increase in temperature of a cell by effectively blocking an IR region having a certain wavelength range, and improve the power generation efficiency of cells.